Now, that being said, none of the starting options constrain us for the rest of the game, or force us to continue their given strategy forever, although some make it easier to do so.
I would go even further than that and say that they don't constrain any of the game, even the start.
The mercantile focus of Demos Drakonia isn't something we particularly focused on during the initial 25 years of Eretria yet if it wins it will have been our primary focus for the following 34 years. Likewise, the massive migration brought about by Demos Antipatria isn't something that was ever much more than an afterthought at best, yet if it wins it will have been a massive focus for Eretria. These choices - none of them - bind us to a future course of action for any period of time, they simply represent the flaw that Eretria believed it had and chose to rectify over this three-decade period.
We
can choose to continue with them, but we can similarly choose to say "job done" and pivot. For example, if we choose Demos Exoria that doesn't compel us to take further military action we could instead simply say 'we're now secure, it's time to focus on trade' and the reverse is true if we take Demos Drakonia. The only exception to this is Demos Antipatria which will require we immediately turn our focus to reform of the metic caste. The others do create issues that have to be solved, but none so urgently.
The counterpoint is that Eretria has now been a fixture for more than two generations of Iapyges, with the Peuketti heavily integrated into our system, the Messapii beaten repeatedly and squeezed between us and Taras, with Egnatia demonstrating again the benefits of cooperation with Eretria, and the Dauni haven't successfully moved against us despite their 34 years of unity.
The Iapyges spent years and an ocean of blood trying to evict Eretria, and it didn't work.
This is true but paints a partial picture at best. I would never argue that any single one of these enemies could utterly dislodge or destroy Eretria, but to dismiss them individually ignores the combined threat and they present and the, frankly awful, strategic situation it puts Eretria in.
The Peuketii are further integrated but, as I said, the threat of the Lucani remains and the integration of the Peuketii doesn't lessen the necessity of going to their aid if the situation is beyond their ability to manage. So to an extent, we have to treat their western border as our own. The Lucani are the threat, not the Peuketti. The Messapii may well find themselves trapped between us and Taras but that doesn't lessen their ability to exploit an opening if we turn to deal with the Dauni, or an enemy further afield, and find ourselves with too few men to secure every border. That would be the sensible thing for them to do after all.
And as for the Dauni themselves, I wouldn't be surprised if they haven't undertaken a massive campaign against us (although if we don't remove them with this vote I wouldn't be surprised if a small war or two was added to the 34 year period), after all they had only just been forced into a confederation by sheer force of will of a single dedicated man. The sensible thing for him to do is to consolidate his position, utterly break his internal rivals and ensure the confederation will last beyond his death. The sensible thing for us to do is destroy them before this can happen and they change from being a newly formed, easily scattered confederation into a singular powerful enemy.
Kerkyra, however, bent us over a barrel almost instantly, due to their fleet, because Eretria's entire territory is coastal and massively reliant on shipping to connect our cities and allow us to rapidly deploy our forces.
They got their way, no doubt about that. But the cause of that was simply that they were so much more powerful than us, in every way. Us starting with a fleet of 22 triremes instead of 18 doesn't to me seem like it will make a massive difference given they had a fleet of (at least) 60 34 years ago. This isn't me saying that we can ignore our fleet and the Adriatic I just don't believe Demos Drakonia - for all its benefits - provides a naval improvement significant enough that Kerkyra (or anyone of that scale) couldn't still do exactly the same thing to us. Honestly, even the Eretria of now wouldn't have the fleet to challenge Kerkyra of then.
Militarily, while Exodia might get us some more experienced hoplites, it also gives us a restless conquered population to suck down our attention and lessen the forces we can effectively deploy elsewhere, whilst Drakonia provides trade wealth to hire mercenaries to buttress our troops if necessary, good fast ships to deploy them where needed, and, at the most basic level, a "spare" 20 men per trireme who could be placed in the land forces as necessary.
A restless, yet fractured and broken, Dauni who have been forced into paying us tribute and providing men is infinitely preferable to a unified, consolidated enemy.